Method of accelerating and improving tanning processes



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atented lune lmi lfl FRIEDRICH JPOSPIECH, OF DRESDEN, GERMANY, ASSIGNORT0 CHIIEMJESCHE FABRIK IOT'JL d6 (30., OF DRIIE$DEN, GERMANY METHOD OFACCELERATING AND IMPRUVING TAN'NING PROGESSES No Drawing. Applicationfiled August 26, 1927, Serial No. 215,761, and in Germany August 21,1926.

The hitherto employed tanning processes in which vegetable tanningprinciples are used are in general, very imperfect, because a very longtime is needed for carrying out such processes and the coloring ofleather produced in the known tanning processes is not alwayssatisfactory. Normally, the tan ning of upper leather, which. has beenpre liminary tanned in the usual ooze of M -2% Be. and has been finishedin an ooze of (5 lie, lasts for at least 12 to 16 days. Severalproposals have been madefor shortening the duration of the process butthe quick-tanning methods hitherto proposed will not however giveentirely satisfactory results, because the grains 'aretanned before theinner parts of the unhaired hides are tanned, whereby the grains aredamaged and the surface of the leather assumes an unattractive look.

According to one quick-tanning method, the hides are treated in tanningliquors, which have been enriched by means of nontanning substances(tannin, gallic acid, resorcin and the like) and are thereupon broughtinto strong tanning liquors, which are supposed to effect a thoroughtanning of the hides in a short time.

According to another proposal, the hides, that is, the grained parts ofthe same are treated with inorganic salts adapted to make the grainsnon-sensitive to the astringent effects of strong tanning liquors(alumen, Glaubers salt, kitchen salt, bitter salt in combination withbichromate, boric acid, oxalic acid, chloride of calcium, hydrochloricaniline).

The first of the processes mentioned is expensive, and on account of thesensitivenessof the employed substances to iron, is not to be dependedupon. Further the tanning lasts for at least 3 to 4 days, because theliquor at the first stages of treatment must not be stronger than 3 to 3156. in order that the grains are not damaged.

The initial treatment with inorganic salts, in accordance with thesecond of the above mentioned proposals, is always risky, becauseconversion with the vegetable tanning agents may take place, whereby thecoloring properties, the softness, the flexibility and the touch of thegrains are ali'ccted in an unfavorable manner. When chronilum salts andalumh num salts are used also the character of the leather is changed,so that a product is obtained, which resembles the so-calledsemichrome-leather.

l have now found, that the above mentioned drawbacks are avoided and theduraqualities superior to the leather hitherto obtained.

Especially suited for the purpose are sul phonic acids which areobtained by condensing naphthalene or ring substitution productsofnaphthalene, or the corresponding sulphonic acids, in the presence ofcondensation or oxidationv agents with alcohols of the aliphatic series,having more than two carbon atoms.

Such substances may, for instance, be produced by converting onemolecule of naphthulene into a mixture of alpha and beta. sulphonicacids and bringing the same into reaction with 2.1 molecules ofisopropyl-alcohol and 221 molecules of concentrated sul 'ihurie acid attemperatures below 100 C. and in the presence of a large quantityofconcentratcd sulphuric acid. The sodium salt, obtained in the usualWay by treating with lime water and boiling the thus obtained sulphonicacid of the condensation product of naphthalene and iso-propyl alcbhol,forms directly a suitable addition for the tanning process to bedescribed.

Instead of naphthalene, other polynuelear aromatic hydrocarbons andsubstitution products of such substances, as for instance, halogen orhydroxy substituted compounds, may be used. Instead of iso-propylalcohol also higher alcohols especially such of the secondary series maybe employed. Further aliphatic and cyclic oletines, such astetradissolved in concentrated sulphuric acid, are well suited for thepurpose in question. The condensation products are amorphous substanceswhich very easily dissolve in water and which as free acids and also asalkali salts possess a considerable moistening and frothing ability.

hydrobeii zol Example 1 kg. of unhaired hides, which are designed fortanned upper leather and which, therefore, have been accordingly treatedin the lime pit, are unlimed and eventually soaked. These hides are notas usual brought into a diluted color solution (tanning liquor of 0.5 to1.5 136.) but are treated with a solution of 2 kg. of one of the abovenamed substances in 300 liters of water for 3 to 4 hours, whereupon thehides are directly brought into a tanning liquor of 4 to 6 B., which issufficiently strong to effect the final tannin The tanning may beperformed in drums or rats. As a tanning agent any vegetable extract ormixture of different extracts may be used. The entire tanning processlasts for 2a to 36 hours.

Ewa-mple 2 100 kg. of unhaired hides, which are designed for bottomleather and have been accordingly treated, are unlimed as possible bymeans of an organic acid (lactic acid, formic-acid, butyric acid or thelike) Thereupon 2 kg. of one of the above named substances are added tothe same bath (or to a fresh bath) and are allowed to act upon thehides. For this purpose small amounts of organic acids may be added anewin order that the unhaired hides may be raised sufficiently. After 3 toL hours the hides can be put into the tanning bath. Any vegetableextract may be used. The extract is chosen in accordance with thepurpose for which the finished product is intended to be used.

Example 3 The tr atment of unhaired hides canalso ire performed in aweak tanning liquor to which 2 kg. of one of the above named substancesare added for each 100 kg. of hides.

I claim 1. A method of accelerating and improving the tanning processeswhen working with vegetable tanning agents, which comprises adding tothe tanning liquor, condensation products of naphthalene sulfonic acidsand alcohols of the alipathic series having more than two carbon atomsin the presence of condensation mediums.

2. A method of accelerating and improving the tanning processes whenworking with vegetable tanning agents, which comprises adding to thetanning liquor sulphonic acids of propylated naphthalene.

FRI EUR [(H POSPIECH.

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